External Connectivity Options in ACI

External Connectivity Options in ACI

In Cisco ACI, any end hosts or network devices that are learned as an endpoint via normal EPG is considered “inside” ACI fabric. ACI provides those endpoints with an exit to other network domains which is referred to as “outside” or External Connections.

This outside network could be another simple Layer 2 network with many non-ACI switches. The connection to such network is called Layer 2 External Network Connectivity, which can be achieved by Layer 2 Out (L2Out) or EPG/VLAN Extension.

Or it could be a Layer 3 network where ACI needs to learn about it via the routing protocol, or static route. This one is called Layer 3 Out (L3Out).

L3Out to external networks have these characteristics:

• Link to network that contains multiple subnets.

• Provide reachability via OSPF, BGP, EIGRP, or static routes.

L2Out or EPG/VLAN Extension to external networks have these characteristics:

• Extend the Layer 2 domain (bridge domain) outside of the Cisco ACI fabric.

• Support VLAN for tagging.

Networks in Cisco ACI